============================================== Extensible and Modular Generics for the Masses ============================================== Extensible and Modular Generics for the Masses (EMGM) is a library for generic programming in Haskell using type classes and a sum-of-products view. ------- Updates ------- emgm-0.3 is the third major release, and it arrives a little over a month after emgm-0.2. Deriving is now greatly improved! Due to recent reports from users, we realized the current implementation just wasn't going to cut it. EMGM already supports a wide range of datatypes, so why not make the deriving code support just as many. Hopefully, it works well for you. Please let us know if your datatype is not supported. There are several new functions in the EMGM family. These include: cast (a type-safe, configurable, generic cast) and everywhere and everywhere' (functions similar to those of the same name in SYB that apply a transformation everywhere a certain type is found). ------- Changes ------- Changes from emgm-0.2 include: *  Improved deriving can now handle datatype collections like this one:   http://www.haskell.org/pipermail/generics/2009-February/000429.html *  cast function

cast :: Rep (Map a) b => a -> b

*  everywhere and everywhere'

everywhere :: Rep (Everywhere a) b => (a -> a) -> b -> b everywhere' :: Rep (Everywhere' a) b => (a -> a) -> b -> b

They both perform transformations on a-values in a b-value. The former does them bottom-up, the latter top-down. The names come from similar functions in SYB that use rank-2 types. Note the difference.

everywhere :: (forall a. Data a => a -> a) -> forall a. Data a => a -> a everywhere' :: (forall a. Data a => a -> a) -> forall a. Data a => a -> a

------------ Known Issues ------------ Due to a problem with the template-haskell package and Cabal, you cannot cabal-install the emgm package with GHC 6.8. However, take heart! EMGM works very well with GHC 6.8. You merely have to download the tar.gz package from Hackage yourself, build it, and install it. Since it doesn't require any dependencies beyond what comes with GHC, installation is a breeze! ------------------- General Information ------------------- Visit the home page:  http://www.cs.uu.nl/wiki/GenericProgramming/EMGM ---------------- General Features ---------------- The primary features of EMGM include: *  Datatype-generic programming using sum-of-product views *  Large collection of ready-to-use generic functions *  Included support for standard datatypes: lists, Maybe, tuples *  Easy to add support for new datatypes *  Type classes make writing new functions straightforward in a structurally inductive style *  Generic functions are extensible with ad-hoc cases for arbitrary datatypes *  Good performance of generic functions The features of this distribution include: *  The API is thoroughly documented with Haddock *  Fully tested with QuickCheck and HUnit *  Program coverage ensures that all useful code has been touched by tests *  Tested on both Mac and Windows systems ------------ Requirements ------------ EMGM has the following requirements: *  GHC 6.8.1 - It has been tested with versions 6.8.3 and 6.10.1 *  Cabal library 1.2.1 - It has been tested with versions 1.2.4.0 and 1.6.0.1. ----------------- Download & Source ----------------- Use caball-install:  cabal install emgm Get the package:  http://hackage.haskell.org/cgi-bin/hackage-scripts/package/emgm Check out the current source with Subversion:  svn checkout https://svn.cs.uu.nl:12443/repos/dgp-haskell/EMGM/trunk Or view it online:   https://svn.cs.uu.nl:12443/viewvc/dgp-haskell/EMGM/trunk/ -------- Examples -------- Check out the examples:  https://svn.cs.uu.nl:12443/viewvc/dgp-haskell/EMGM/trunk/examples/ -------------- Bugs & Support -------------- Report issues or request features:   http://code.google.com/p/emgm/issues/list Discuss EMGM with the authors, maintainers, and other interested persons:  http://www.haskell.org/mailman/listinfo/generics ------- Credits ------- The research for EMGM originated with Ralf Hinze. It was extended with work by Bruno Oliveira and Andres Löh. More details of the library functionality were explored by Alexey Rodriguez. We are very grateful to all of these people for the foundation on which this library was built. The current authors and maintainers of EMGM are: *  Sean Leather *  José Pedro Magalhães *  Alexey Rodriguez *  Andres Löh